The present invention relates to an ink set, an ink cartridge, and a recording method using same, and a recording material and recording apparatus therefor. More particularly, the present invention relates to an ink set and ink cartridge which allow color printing of an image having an excellent color reproduction with a plurality inks using an ink jet recording apparatus and provide a good discoloration resistance and color developability, a recording method using the ink set and ink cartridge, a recorded material thus obtained, and a recording apparatus therefor.
As well known, an ink jet recording method is a printing method which comprises allowing ink droplets to fly so that they are attached to a recording medium such as paper to effect printing. This printing method allows fast and easy printing of a high resolution and quality image using an inexpensive apparatus. In particular, in the art of color printing with a plurality of inks (magenta, cyan, yellow inks), this printing method has been recently under technical development to provide an image forming method substitute for photography.
An ink normally comprises water as a main component having a colorant component, a wetting agent for preventing clogging such as glycerin, a penetrating agent, etc. incorporated therein. As the plurality of color inks to be used in the ink jet recording method there are used a dye ink (ink comprising a xe2x80x9cdyexe2x80x9d incorporated therein as a colorant) and a pigment ink (ink comprising a xe2x80x9cpigmentxe2x80x9d incorporated therein as a colorant).
(Problem 1 of the Background Art)
As the colorant to be incorporated in the dye ink there is used particularly a xe2x80x9cwater-soluble dyexe2x80x9d from the standpoint of advantages of high image quality such as high color saturation and color reproducibility, abundance in colorants which can be used, solubility in water, reliability in resistance to clogging, and ability to represent a color having a good transparency on a recording medium.
However, the dye ink is disadvantageous in that it is inferior to the pigment ink in respect to properties such as light fastness and water fastness. This difficulty becomes remarkable particularly in a low image density range (so-called highlight range).
On the other hand, the pigment ink is advantageous in that it allows printing of characters and images with little bleeding as compared with the dye ink. Further, a pigment ink is excellent in light fastness and water fastness as compared with a dye. In recent years, the use of a pigment as a colorant for ink jet recording ink has been studied for the purpose of improving light fastness and water fastness.
However, the pigment ink is disadvantageous in that it is inferior to the dye ink in respect to color developability. Further, since a pigment is normally insoluble in water, in order to incorporate a pigment in an aqueous ink, the pigment has to be uniformly dispersed in water in the form of mixture with a resin called dispersant to provide the resulting ink with a prolonged reliability. However, when all colors are provided by pigments, it is disadvantageous in that a desired dispersion stability can hardly be secured.
Further, unlike one obtained with an aqueous ink comprising a dye incorporated therein, a printed matter obtained with an aqueous ink comprising a pigment incorporated therein has some pigment left on the surface thereof and thus can hardly resist scratching. Moreover, when all colors are provided by pigments, the resulting inks exhibit a poor transparency (color developability) and hue and hence a low color reproducibility.
In an attempt to eliminate these difficulties and disadvantages, the combination of a dye ink and a pigment ink has heretofore been proposed. For example, JP-A-5-148441 (The term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses a xe2x80x9crecording liquid suitable for ink jet printer, and ink jet recording method using samexe2x80x9d involving the use of specific xe2x80x9cdye and pigmentxe2x80x9d as colorant for magenta ink. Further, JP-A-5-155004 discloses a xe2x80x9ccolor image forming method by ink jet recording methodxe2x80x9d involving the use of a specific dye as colorant for yellow ink and a specific pigment as colorant for magenta ink and cyan ink. Moreover, JP-A-5-155005 discloses a xe2x80x9ccolor image forming method by ink jet recording methodxe2x80x9d involving the use of a specific dye as colorant for yellow ink and cyan ink and a specific pigment as colorant for magenta ink.
However, none of the approaches disclosed in the above cited patents can eliminate the foregoing difficulties and disadvantages. In particular, the problem that a dye ink is remarkably disadvantageous in properties such as light fastness and water fastness in a low image density range (highlight range) cannot be solved.
(Problem 2 of the Background Art)
Among the color dye inks (yellow, magenta, cyan), the magenta ink is particularly disadvantageous in that it exhibits a deteriorated light fastness. Thus, when irradiated with light, the resulting image exhibits an ill-balanced hue and thus shows a remarkably deteriorated quality. Further, discoloration is accelerated not only in single magenta color but also in blue color represented by magenta and cyan in combination to cause drastic deterioration of image quality.
Further, when inks having the same hue but different densities (dark-colored and light-colored inks) are used to reduce the graininess on a range from a low image density range (highlight range) to middle tone range, a photograph-like image can be obtained. However, the light-colored ink exhibits a far low light fastness than the dark-colored ink). The light-colored magenta ink is remarkable in this tendency. Further, the area having magenta and cyan in mixture can undergo rapid discoloration due to deterioration by light. This in presumably attributed to harmful radicals or active oxygen (singlet oxygen), etc. produced by light.
(Problem 3 of the Background Art)
As the foregoing xe2x80x9cink jet recording mediumxe2x80x9d on which image recording is effected with a water-soluble dye there is known an xe2x80x9cink jet recording medium having a porous ink-receiving layer provided on a substratexe2x80x9d which allows printing of an image having an excellent water fastness and a high quality that can dry quickly.
However, a recorded material obtained by ejecting the foregoing water-soluble dye onto an ink jet recording medium having a porous ink-receiving layer provided an a substrate is subject to discoloration due to gases such as ozone (O3), nitrogen oxide (NOx) and sulfur oxide (SOx) contained in the air when the dye contained in the ink as a colorant is brought into contact with the atmosphere because the ink-receiving layer is porous. In particular, among the color dye inks (yellow, magenta, cyan), some cyan dyes, though having a high water fastness and light fastness, exhibit a low gas resistance (C.I. direct blue 86, 199, etc.). Thus, there arises a problem that an image obtained with such a cyan dye having a copper phthalocyanine skeleton undergoes deterioration due to oxidation and reduction by gases and hence an ill-balanced hue that causes the image to show a remarkable deterioration. This problem becomes remarkable particularly in a low image density range (highlight range).
The inventors made extensive studies of an ink jet recording method using color inks, particularly a plurality of inks having different densities but the same hue (dark-colored ink and light-colored ink). As a result, it was found that the combination of specific pigment ink (at least one of light-colored inks is an ink containing a pigment as a colorant) and dye inks makes it possible to provide a high image quality, a high rub fastness and a high light fastness at the same time (A high quality image and a high rub fastness can be realized and discoloration can be effectively inhibited.). The present invention has thus been completed.
In other words, the present invention has been firstly worked out in the light of the foregoing xe2x80x9cproblems 1 to 3 of the background artxe2x80x9d. An object of the invention is to provide an ink set which gives a printed image having an excellent color reproduction and exhibits a good discoloration resistance and color developability (hereinafter referred to as xe2x80x9cfirst objectxe2x80x9d).
In order to accomplish the first object of the invention, the first ink set of the invention is an xe2x80x9cink set comprising a dye ink and a pigment ink in combination, characterized in at least one hue contains a plurality of inks having the same hue but different densities for at least one hue and at least one of the inks having the same hue has a low density and comprises a pigment incorporated therein as a colorantxe2x80x9d. Thus, the use of a xe2x80x9cink having a low density (light-colored ink)xe2x80x9d containing a pigment as a colorant makes it possible to improve various properties such as light fastness and water fastness particularly in a low image density region (highlight region).
Secondly, the present invention has been worked out in the light of the foregoing xe2x80x9cproblems 1 to 3 of the background artxe2x80x9d, particularly the foregoing xe2x80x9cproblem 2 of the background artxe2x80x9d. Another object of the invention is to provide an ink set and an ink cartridge for giving a printed image having excellent color reproduction and rub fastness which undergoes no deterioration due to discoloration, particularly of blue color represented by magenta and cyan in combination, not to mention of magenta alone, to provide a recorded material having an excellent light fastness, and an ink jet recording method using the ink set and ink cartridge, an recorded material thus obtained, and a recording apparatus therefor (hereinafter referred to as xe2x80x9csecond objectxe2x80x9d).
In order to accomplish the second object of the invention, the second ink act of the invention is an xe2x80x9cink having a plurality of magenta inks having the same hue but different densities for at least one hue, characterized in that at least light-colored magenta ink among the plurality of magenta inks comprises a pigment incorporated therein as a colorant and the other inks of a different hue each comprise a dye incorporated as a colorantxe2x80x9d. In this arrangement, an effect can be exerted of realizing an ink jet recording method of forming a color image having a high quality and rub fastness which undergoes no discoloration due to light.
The ink cartridge for accomplishing the second object of the invention is an xe2x80x9cink cartridge comprising a plurality of magenta inks having different densities and other inks received integrally as independently at least partly therein, characterized in that at least light-colored magenta ink among the plurality of magenta inks contains a pigment as a colorant and the other inks of a different hue contain a dye as a colorantxe2x80x9d. In this arrangement, an effect can be exerted of allowing printing of a color image having a high quality and rub fastness which undergoes no discoloration and giving an ease of handling of ink.
The ink jet recording method, recorded material thus obtained and recording apparatus therefor for accomplishing the second object of the invention are characterized by the use of the foregoing second ink set. In this arrangement, an effect can be certainly exerted of forming an image having a good quality, improving rub fastness and inhibiting discoloration. Further, the mounting of the ink cartridge on a cartridge can be made easily.
As mentioned above, in accordance with the invention for accomplishing the second object of the invention, color printing is effected using a plurality of magenta inks having different densities and other inks wherein at least light-colored magenta ink among the plurality of magenta inks comprises a pigment incorporated therein as a colorant and the other inks comprise a dye incorporated therein as a colorant, making it possible to exert an effect of keeping image quality such an color reproduction good, rendering the image resistant to scratch and making up for defects in light fastness of magenta color and blue color comprising magenta and cyan in combination to effectively inhibit discoloration. As the dark-colored ink (dark-colored cyan and dark-colored magenta) there is preferably used a dye ink. Such a dye ink is also advantageous in that a wider range of color reproduction can be realized.
Thirdly, the present invention has been worked out in the light of the foregoing xe2x80x9cproblems 1 to 3 of the background artxe2x80x9d, particularly the foregoing xe2x80x9cproblem 3 of the background artxe2x80x9d. A further object of the invention is to provide an ink set and ink cartridge capable of providing an image having a high quality, a high water fastness and a high light fastness as well as a high gas resistance upon recording on an ink jet recording medium having a porous ink-receiving layer provided on a substrate, and an ink jet recording method using the ink set and ink cartridge, a recorded material thus obtained and a recording apparatus therefor (hereinafter referred to as xe2x80x9cthird objectxe2x80x9d).
In order to accomplish the third object, the ink set of the invention is an xe2x80x9cink comprising a plurality of cyan inks having the same hue but different densities wherein at least light-colored cyan ink among the plurality of cyan inks comprises a pigment incorporated therein as a colorant and the other inks of a different hue comprise a dye incorporated therein as a colorantxe2x80x9d. The ink set is an xe2x80x9cink set for recording on an ink jet recording medium having a porous ink-receiving layer provided on a substratexe2x80x9d. In this arrangement, the following effects can be exerted.
A cyan ink comprising a dye incorporated therein as a colorant undergoes discoloration due to gases such as ozone (O3), nitrogen oxide (NOx) and sulfur oxide (SOx) more remarkably than other dye color inks (magenta, yellow, etc.). However, a plurality of cyan inks having different densities wherein at least light-colored cyan ink comprises a xe2x80x9cpigmentxe2x80x9d incorporated therein as a colorant undergoes suppressed discoloration. The use of this xe2x80x9cink set comprising a light-colored cyan ink containing a pigmentxe2x80x9d makes it possible to exert an effect of providing an image having a high quality, a high water fastness and a high light fastness as well as a high gas resistance upon recording on an ink jet recording medium having a porous ink-receiving layer provided an a substrate.
In the foregoing xe2x80x9cink set comprising a light-colored cyan ink containing a pigmentxe2x80x9d, the pigment is preferably C.I. pigment blue 15:3. C.I. pigment blue 15:3 is a colorant having a high water fastness, a high light fastness and a high gas resistance and thus particularly can provide an image having a high water fastness, a high light fastness and a high gas resistance.
As the colorants for the foregoing light-colored cyan ink there are preferably used a dye and a pigment in combination. The combined use of a pigment and a dye makes it possible to provide a better color developability than single use of pigment and thus obtain a high quality image.
The use of two or more cyan inks having different densities makes it possible to certainly realize a color containing cyan and thus obtain a high precision image.
The ink cartridge for accomplishing the foregoing third object is an xe2x80x9cink cartridge comprising a plurality of cyan inks having different densities and other inks received integrally or independently at least partly therein, characterized in that at least light-colored cyan ink among the plurality of cyan inks contains a pigment as a colorant and the other inks of a different hue contain a dye as a colorantxe2x80x9d. In this arrangement, an effect can be exerted of providing an image having a high quality, a high water fastness and a high light fastness as well as a high gas resistance as mentioned above.
In the foregoing ink cartridge, the pigment to be incorporated in the light-colored cyan ink is preferably C.I. pigment blue 15:3, and as the colorants to be incorporated in the light-colored cyan ink there are preferably used a pigment and a dye in combination. In this arrangement, an ink cartridge can be provided having the same effect as mentioned above.
The ink jet recording method, recorded material thus obtained and recording apparatus therefor for accomplishing the foregoing third object are characterized by the use of the foregoing third ink set. In this arrangement, an ink jet recording method, recorded material thus obtained and recording apparatus therefor can be provided having the same effect as mentioned above.
Fourthly, the present invention has been worked out in the light of the foregoing xe2x80x9cproblems 1 to 3 of the background artxe2x80x9d, particularly the foregoing xe2x80x9cproblems 2 and 3 of the background artxe2x80x9d. A further object of the invention is to provide an ink set and ink cartridge which can provide an image having a high quality, a high water fastness and a high light fastness as well as a high gas resistance, an ink jet recording method using the ink set and ink cartridge, a recorded material thus obtained, and a recording apparatus therefor (hereinafter referred to as xe2x80x9cfourth objectxe2x80x9d).
In order to accomplish the foregoing forth object, the fourth ink set of the invention is an xe2x80x9cink comprising a plurality of magenta inks and cyan inks each having the same hue but different densities, characterized in that at least light-colored magenta ink and cyan ink among the plurality of magenta inks and cyan inks each comprise a pigment incorporated therein as a colorant and the other inks each comprise a dye incorporated therein as a colorantxe2x80x9d. In this arrangement, an ink set for accomplishing the foregoing second and third objects and having both the effects exerted by the foregoing second and third ink sets in combination can be provided.
The ink cartridge for accomplishing the foregoing fourth object is an xe2x80x9cink cartridge comprising a plurality of magenta inks and cyan inks each having different densities but the same hue, characterized in that at least light-colored magenta ink and cyan ink of the plurality of magenta inks and cyan inks each comprise a pigment incorporated therein as a colorant and the others inks each comprise a dye incorporated therein as a colorantxe2x80x9d.
Further, the ink jet recording method, recorded material thus obtained, and recording apparatus therefor for accomplishing the foregoing fourth object are characterized by the use of the foregoing fourth ink set.
As mentioned above, the invention for accomplishing the foregoing fourth object involves the use of a plurality of inks having the same hue the light-colored ink (particularly the ink having the lowest density in the same hue) among which comprises a pigment incorporated therein, making it possible to improve the light fastness in a low image density range where the light-colored ink is mainly used. Further, since the dark-colored ink (ink having the highest density) comprises a dye incorporated therein, a sharp image having a good transparency can be obtained in a high image density region.
The term xe2x80x9cink comprising a pigment incorporated thereinxe2x80x9d as used herein is meant to include both xe2x80x9cink comprising a pigment alone incorporated thereinxe2x80x9d and xe2x80x9cink comprising a pigment and a dye incorporated therein in combinationxe2x80x9d.